Smartphones are increasingly being used with “visual search” applications. One visual search application decodes digital watermark data steganographically encoded (i.e., hidden) in printed imagery (such as in a magazine or on product packaging) and enables the phone to link to associated information and services. Examples of digital watermark technology, and visual search applications, are detailed in Digimarc's patents U.S. Pat. Nos. 6,483,927, 6,590,996 and 6,947,571, and in application Ser. No. 12/774,512 (filed May 5, 2010), Ser. No. 12/797,503 (filed Jun. 9, 2010), and Ser. No. 13/011,618 (filed Jan. 21, 2011).
Perspective distortion can sometimes interfere with proper decoding of digital watermark data. That is, if a watermarked object is imaged by a smartphone at a relatively large off-axis angle (e.g., greater than 15 or 30 degrees), the hidden watermark data may be sufficiently distorted by the perspective viewing angle that the decoding algorithm does not recognize it.
Relatedly, if a watermarked object is imaged from too-great or too-close a distance, the scale of the embedded watermark in the captured imagery may be so different than what is expected that the decoding algorithm again cannot recognize it. (This may be regarded as another type of perspective distortion.)
A related concern is consumer confusion. If a consumer uses a smartphone to image a magazine page, and no watermark is promptly detected, is it because the page does not include a watermark to which the smartphone should respond? Or is it because the magazine page is presented with an unsuitable perspective?
Accordingly, it is desirable to assist the consumer in capturing imagery that has relatively small perspective distortion (e.g., less than 15 or 30 degrees) or, alternatively, to warp captured imagery so as to un-do most of its original perspective distortion. Relatedly, it is desirable to guide the consumer in capturing imagery of a suitable scale state for the detector (or, alternatively, to re-size captured imagery so as to change its scale state to a suitable value).
In accordance with one aspect of the present technology, the perspective of an object relative to a smartphone is determined from a quick wave of the smartphone over the object. Data captured in such action is used to discern, at least partially, a geometrical relationship between the smartphone and the object. This geometrical information can include data about the off-axis viewing angles, and/or the distance to the object. Such information can then be used to help guide the user in acquiring imagery with reduced perspective distortion, or to process captured imagery to mitigate such distortion.
Furthermore, the determined geometrical information can include data about the size and shape of the object. For example, the object may be a curled or rolled newspaper. Its geometry can be discerned, and such deformation can be reversed from captured imagery in the same way that perspective distortion can be reversed.
Once the smartphone is in a suitable geometric pose relative to the object (or once the perspective geometry is characterized so that suitable corrective image processing can be applied), the smartphone will promptly detect the watermark (e.g., in less than 0.5, 1, or 2 seconds)—if one is present. If no watermark is detected within such period, the phone may signal to the user—confidently—that there is no watermark in the captured imagery. Such arrangement provides an enhanced experience to the consumer—redressing the perspective difficulty, and eliminating the uncertainty of the prior art.
The foregoing and other features and advantages of the present technology will be more readily apparent from the following detailed description, which proceeds by reference to the accompanying drawings.